Glue or not to glue

[Jake]

You won't find any recommendation from an informed UK source to glue exterior T&G together. California is (legendarily) a rather different climate.

 

[Ed Weber]

I still don't understand what your sticking point is about T&G.
What if it was just a wide (glued together) flat panel? Would that make a difference in your mind?

With all due respect, to the "informed UK sources";
This is only T&G for the appearance sake, it really makes no difference what the edge profile is. It's just a wide frame and panel construction.
The T&G really does not come into play, I'm not laying a traditional floor, it's a primarily decorative panel.
I'm not sure what is so difficult to wrap you head around.
None of you have yet to tell me what woodworking "rules" I've broken. All I hear is fear mongering that it will fail and so far after a decade it hasn't.
End of

 

[Blackswanwood]

I still don't understand what your sticking point is about T&G.

There isn’t a sticking point - we’re not using glue …

 

[Sgian Dubh]

So when the piece in the center needs to expand, it has to push both sides 500mm?
Why would it catch? Why would it split? There is nothing holding it in position other than gravity and a little friction. BTW this is 1800mm and has moved freely for 10 years.

This is nothing more than a basic frame and panel construction, some of the members don't seem to understand that and think I've broken some long held woodworking rule.
In my (exaggerated) example, it's nothing more than a large FLOATING panel that just happens to be made of several pieces glued together. The same process used in a much narrower gate would pose no problems as many seem to think.
I did not break the frame and panel rules. Please don't call the wood police.

Your approach is somewhat unconventional, although your understanding of wood expansion/contraction is good. It's true that total expansion and shrinkage of, say, 10 tangentially sawn red pine boards 100 mm wide at their driest in service will be the same whether joined together into one wider panel of 1000 mm wide or individually. In this example let's say each board expands and contracts by 2 mm over the seasons, i.e., in this case between 100 and 102 mm meaning a total range of movement of 20 mm annually. That is, as you evidently understand, 10 boards X 2 mm of expansion/contraction = 20 mm, or those 10 boards glued together to make a 1000 mm wide panel which would result in 20 mm expansion/contraction.

Just for fun I did some sums using your 1800 mm wide panel made out of tangentially sawn (T&G boards are always tangentially sawn) red pine (pinus resinosa) native to NE America, [no idea what you actually used] varying between 14 and 20% MC, fairly typical for wood used externally here in the UK. It results in panel size change of approximately 26 mm, or about 2 mm per board for each of the 14 boards in your panel. Assuming expansion/contraction of the panel occurs from its centre point the depth of the groove at either edge would need to be a minimum of 13 mm to avoid the edge of the panel popping out of its groove. Most workers would aim for a greater margin of safety than this, e.g., a groove perhaps 18 - 20 mm deep, or they'd do the conventional thing, and not glue the tongues and grooves together and fit the boards with a bit of wriggle room at each of their edges, plus ideally, fixed at each board's centre point, and into a groove if the boards go into a groove; not all do go into grooves, because some go into rebates, and some are just laid over some framing.

Having said all the above, I don't know what wood species you used in your photographed piece, therefore nor do I know the typical shrinkage/expansion factor I needed to plug into the formula I use for the calculation I can undertake, and I don't know the typical range of MC your piece experiences there in California.

Still, it's interesting that you've got away without a failure with one wide panel as you have for the last ten years. Sometimes the unconventional works. Slainte.

 

[Doug71]

You can almost tell what the weather is doing by the T&G in my driveway gates, I'm always amazed how much it moves.

We have had a nice day or two here in Yorkshire and the gaps between the boards average about 3mm.

The gaps will get wider over the next few days with the warm weather forecast, when we have a few wet days the gaps soon fully close up and as @niall Y mentioned I get the unsightly curling groove thing.

There are 18 boards on each gate so 19 gaps, allowing for only 3mm movement per board would mean a solid panel would increase in width by 57mm (deep grooves needed!).

I will keep updating this thread with photos of my gap size for those interested 🤣

 

[peter-harrison]

So when the piece in the center needs to expand, it has to push both sides 500mm?
Why would it catch? Why would it split? There is nothing holding it in position other than gravity and a little friction. BTW this is 1800mm and has moved freely for 10 years.

This is nothing more than a basic frame and panel construction, some of the members don't seem to understand that and think I've broken some long held woodworking rule.
In my (exaggerated) example, it's nothing more than a large FLOATING panel that just happens to be made of several pieces glued together. The same process used in a much narrower gate would pose no problems as many seem to think.
I did not break the frame and panel rules. Please don't call the wood police.

As has been said above, the point of T&G is to have a lot of fairly narrow boards that are linked in one plane but not in others, so they can do their own thing. You may fit them nicely to a groove when they're fresh out of the thicknesser, but the moment they get a bit of water on them some of them are likely to cup, which will have the effect of jamming them in the groove. If you glue them all together, and you have two bits of T&G jammed in the groove, then it's a match between the strength of your glue joints and the force needed to move them along the groove.

 

[Jacob]

Let me be perfectly clear the T&G boards are glued to each other NOT the frame. It's nothing more than a large floating panel, no different than a solid piece. There is no reason that it should fail.

There is if there is major change in humidity. From very dry to very wet you'd expect a total horizontal movement of an inch or more in such a large panel, if that was possible at all in such a long slot. I'd expect it to snag and split.
Maybe you water the plants enough to keep the boards in a fairly steady state?
My worst experience of panel movement was in a set of georgian style internal doors i.e. no muntin but wide panels top and bottom, 20" or so. The wood was dry and I left a normal amount of clearance for movement. Soon after the room was completely re-plastered which I wasn't expecting, and hence with the doors and window shut 100% relative humidity as the plaster dried.
The panels expanded enough to force the stiles away from the rails, opening gaps leaving me with a major rebuild problem. I must have skimped on the glue or the doors might have self destructed beyond rebuilding! Never again.

 

[Jacob]

......

Just for fun I did some sums using your 1800 mm wide panel made out of tangentially sawn (T&G boards are always tangentially sawn) ...

Same as "slab sawn"? It's all I ever see in T&G or any plain boards in N European redwood. Heart wood and knots to the middle, sap wood to the edges

 

[Sgian Dubh]

Same as "slab sawn"?

Yes, and also commonly called through and through, slash sawn, plain sawn and crown cut. Slainte.

 

[Agent_zed]

I still don't understand what your sticking point is about T&G.
What if it was just a wide (glued together) flat panel? Would that make a difference in your mind?

With all due respect, to the "informed UK sources";
This is only T&G for the appearance sake, it really makes no difference what the edge profile is. It's just a wide frame and panel construction.
The T&G really does not come into play, I'm not laying a traditional floor, it's a primarily decorative panel.
I'm not sure what is so difficult to wrap you head around.
None of you have yet to tell me what woodworking "rules" I've broken. All I hear is fear mongering that it will fail and so far after a decade it hasn't.
End of

I'm not sure why people are so anti your suggestion. I can fully understand your point. If you look at front doors in the uk, you'll often find ones like this https://www.doorsonlineuk.co.uk/ext.../stable-9l-arched-mt-hardwood-external-doors/ and it certainly doesn't look like T+G floating in the bottom panel. Instead it is basically what you have done which is create a single panel from separate pieces, as there is no way they have a ~28inch plank to create it in one piece.

Doesn't seem to be a huge issue either way

 

[Sam Kilby]

If (and it’s a fairly big if, lots of big door factories would use for example a veneer pressed ply panel for a fake floating panel effect or even a thicker “constructional veneer” sandwich which is at least thick enough to allow for any machining ) it is boarded up then it becomes a “floating panel”.. which is fine and can be done, just needs deeper and likely also less tight grooves or rebates to run into, and is more likely to want to cup and bind in an environment like an external door.
Also if it is a floating panel, it’s movement could also be attested centre top and bottom, either with glue or through dowels so it grows and shrinks from a fixed central point.

 

[John Brown]

Making a solid panel will make the entire structure stiffer.
There are many ways to approach this.
Also, you need the same amount of room to accommodate movement of several small panels, as you do for 1 large panel, the panel is the same size no matter how you divide it up.

Yes, but if unglued it's spread over more gaps...

 

[Doug71]

I'm not sure why people are so anti your suggestion. I can fully understand your point. If you look at front doors in the uk, you'll often find ones like this https://www.doorsonlineuk.co.uk/ext.../stable-9l-arched-mt-hardwood-external-doors/ and it certainly doesn't look like T+G floating in the bottom panel. Instead it is basically what you have done which is create a single panel from separate pieces, as there is no way they have a ~28inch plank to create it in one piece.

Doesn't seem to be a huge issue either way

It says the door in the link is constructed of engineered hardwood, this can mean ply or even MDF, I very much doubt the panel in that door is solid wood.

 

[Agent_zed]

It says the door in the link is constructed of engineered hardwood, this can mean ply or even MDF, I very much doubt the panel in that door is solid wood.

maybe, maybe not. My front door is definitely solid although smaller panels. each panel is ~8inches and is made of more than one piece glued together. Been there way before I got the house 10 years ago and hasn't had a problem despite me not doing a lot of maintenance on it.

 

[Rewby]

There's a world of difference between gluing square edge boards together to make a panel and gluing T&G boards together.You don't glue T&G boards it will split at the tongue.
Probably one of the first things you are taught in a joiners shop as apprentices.